The study, which is being published Wednesday in The Journal of the American Medical Association, found that a predecessor to accountable care organizations achieved particular savings in caring for patients eligible for both Medicare and Medicaid. In the predecessor program, a Medicare experiment that ran from 2005 to 2010, 10 doctors groups from around the country received bonus payments if they met quality targets and achieved lower cost growth compared with Medicare spending on other patients in their region. The study, conducted by researchers from the Dartmouth Institute for Health Policy and Clinical Practice, found that the growth in spending per "dual eligible" patient slowed by $532 a year, or 5 percent, after doctors groups joined the demonstration program.